Agricultural and/or industrial irrigation systems are known in the art, which comprise a line for supplying an irrigation liquid, e.g. water, connected to a plurality of sprinkler devices for distributing a jet of such liquid to a soil portion to be irrigated.
A peculiar characteristic of these systems is that they distribute a constant amount of liquid to a given soil portion, to irrigate it in a substantially uniform manner.
Furthermore, the sprinkler devices may be either stationary, to always irrigate the same soil portion, or movable relative to the supply conduit for substantially constant-speed sweeping of a given cultivated surface.
Almost all the sprinklers for use in irrigation systems allow the jet nozzle to be changed or varied to adapt liquid distribution to the needs of the particular soil or crop.
Nevertheless, uniform liquid distribution requires a substantially constant jet pressure, regardless of the nozzle that is mounted to the sprinkler.
Therefore, a pressure regulating device, connected to the supply line, is often installed upstream from the nozzle, with liquid having a relatively constant pressure value at its outlet.
These devices have a fluidically connected tubular closure member therein, and a liquid stagnation chamber located proximate to the outlet and adapted to temporarily contain the liquid that builds up before being delivered through the nozzle. The backpressure generated in the chamber causes the closure member to move under the force exerted thereupon by a liquid fraction circulating in a calibrated orifice. The axial movement of the closure member changes the flow rate of the liquid circulating through the inlet and accordingly maintains the outlet pressure at a constant level.
U.S. Pat. No. 7,048,001 relates to a pressure regulating device that is specially designed to prevent grass or other materials to stop the movement of the closure member, thereby causing sudden pressure drops.
This device has a tubular body with a fluid inlet and a fluid outlet, connected via a central passage with a tubular plunger slidingly moving therein. A seat is also formed in the passage, facing one end of the plunger and adapted to cooperate therewith to change the amount of liquid circulating in the passage.
The seat radially projects toward the center of the passage and is supported by a single strut which extends from an annular member supported in the tubular body adjacent to the fluid inlet. The strut is also placed upstream from a face which is also placed upstream from the support ring.
A first drawback of this arrangement is that the pressure of the fluid that comes out of this device may be affected by non-negligible deviations from the desired value during operation of the system.
This is because the provision of a single support strut imparts a given elasticity to the seat, that can lead to a change of its axial position when the fluid in the supply circuit generates water hammers or when foreign matters such as grass, leaves, stones or the like.
Nevertheless, in addition to being flexible, the seat is also relatively fragile because it may be broken or damaged if a great stress is transferred thereupon.
A further drawback of this solution is that this seat is rigidly joined to an annular support that is distinct and separate from the enclosure of the device, which makes the assembly of the latter relatively complex, due to the great number of its parts.
Furthermore, this configuration increases both the manufacturing costs and the assembly time for the device.
Also, another drawback of this arrangement is that this device requires great care during inspection, as external pointed tools are used therefor, which may damage the seat.
Furthermore, in order to remove impurities such as grass, soil or the like, which build up at the seat during operation of the system, the device is often washed with an abrasive liquid, that might cause wear of the seat, thereby causing an undesired change of liquid delivery pressure.